Black Grass Bug
Black grass bugs are small, black true bugs that are native to the western rangeland and can cause considerable damage to certain range grasses. Several species of black grass bugs can be found in Colorado, with the most common being Labops hesperius. A second species, Irbisia brachycera may be locally abundant as well. Adult black grass bugs are ¼ inch in length and mostly black (I. brachycera) with tan margins of their wings and abdomen (L. hesperius). Immature stages are similar in appearance to adults, but smaller. One generation of black grass bugs occurs per year.
Whitney Cranshaw, Colorado State University, Bugwood.org.
Black grass bug on light green leaf.
Frank Peairs, Colorado State University, Bugwood.org
Black grass bug.
Whitney Cranshaw, Colorado State University, Bugwood.org
Black grass bug on green leaf.
- Black grass bugs are small, black true bugs that are native to the western rangeland and can cause considerable damage to certain range grasses
- Injury is most pronounced on the upper surface of the leaf and may look straw-colored, similar to frost damage
- Injury may make grass unpalatable to cattle or prevent seed formation
Black grass bugs have a wide range of hosts, but prefer grasses, with a preference for wheatgrass. Most damage in the spring with their piercing/sucking feeding. White spots appear on the leaf surface at the site of feeding soon after. Injury is most pronounced on the upper surface of the leaf and may look straw-colored, similar to frost damage. High level of injury to the leaves can make the grass unpalatable to cattle. Heavy infestations may prevent seed formation.
Scouting for black grass bugs should occur in the spring as temperatures warm and the eggs begin to hatch. Sweep net is commonly used to sample the bugs. Action thresholds for black grass bugs are not defined, however. Insecticides will kill the adult insects but will have no effect on eggs laid in grass stems. If enough eggs are present, a re-infestation may occur in the next growing season. One well timed application of insecticide may reduce bug numbers to a non-economic level for many years. Timely grazing or burning dead grasses in the fall are management techniques that destroy black grass bug eggs and may limit the need of chemical control. Mowing and removal of hay may be a management technique for reducing the number of eggs in some circumstances.